Low-cost, high-performance W-band LNA MMICs for millimeter-wave imaging

The main limitation to the sensitivity of a radiometer or imager is its equivalent noise temperature, T-e. Placing a low noise amplifier (LNA) at a radiometer's front end can dramatically reduce T-e. LNA performance has steadily improved over recent years, and here we report on a W-band LNA with the lowest T-e measured at loom temperature. Furthermore, we present statistical RF data showing high yield and consistency for future high volume production that is needed for commercial radiometric imaging array applications such as security screening, aircraft landing, and other systems. Previously, the lowest noise room temperature (290 K) W-band LNA demonstrated 3.3 dB noise figure (NF) (T-e = 330 K) with 20 dB associated gain(1), although the average NF was 4.4 dB (T-e > 500 K) over the 92 to 96 GHz band. Here we present measurements of an InP-based 0.1 mu m HEMT 4-stage LNA MMIC (86LN3) with an average NF of 2.5 dB (T-e = 225 K) and average gain of 30 dB over a 76 to 96 GHz band. This is the lowest reported room temperature LNA noise figure to the authors' knowledge, and demonstrates the performance capability of this HEMT technology. Two other, more conservative designs (70LN3A and 86LN1A) were chosen for higher-volume production with 24 dB gain, 3.2 dB NF (T-e = 315 K) and 21 dB gain, 2.9 dB NF (T-e = 275 K) respectively at the center of the band, 85 GHz. These LNAs were fabricated on 3 " wafers containing 1700 die with an average DC yield of 70% and 98% of DC good die passing RF screening.